This invention relates to the preparation of an oil-in-water emulsion suitable for the preparation of dairy or dairy-like products.
As is well-known, milk is an oil-in-water emulsion, the discontinuous phase being formed by milk fat and the continuous (aqueous) phase containing numerous substances, particularly proteins and sugars. Milk is the raw material for the preparation of numerous dairy products in which physicochemical changes are effected by the action of enzymes and/or microorganisms.
The problem of using milk as a raw material is that in view of its relatively short storage life the place of treatment must be near the place of production. Especially in very large countries, having regard to logistic problems, it would therefore be desirable to enable a more decentralized treatment of milk or milk-like products, e.g. near large population centres.
It is therefore an object of the invention to prepare an oil-in-water emulsion using as many standardized raw materials as possible and obtaining an emulsion which, as for the dairy-like products to be prepared therefrom, shows the greatest possible similarity with natural milk and which emulsion, together with milk, wholly or partly skimmed milk or reconstituted milk, can be processed to dairy or dairy-like products.
The prior art shows that attempts to prepare emulsions of the type in question have been made earlier. These attempts, however, have not led to the desired result, inter alia owing to the occurrence of organoleptic and/or stability problems.
Thus, European patent application 0 304 119 describes a process for the preparation of a semihard to hard cheese product, which comprises preparing an oil-in-water emulsion from a partially unsaturated fat and an aqueous phase, followed by preparing cheese, chiefly in a manner as known for the conventional cheese preparation from milk. As is established again in that patent application, the problem arising in the preparation of cheese in the manner described is that the taste of the resulting cheese is absolutely insufficient. For this reason the above application proposes that after the resulting curd has been separated from the whey, 0.1-2.5 wt. % of a concentrate of flavourings is added to the curd. However, it is known to be difficult to obtain a well balanced cheese taste, so that the final product will soon call forth an unnatural taste sensation and particularly a bitter taste sensation. Moreover, the examples of that patent application show that the process described was only used for the preparation of Cheddar cheese. This is understandable because Cheddar cheese is a type of cheese for which the soured cheese curd is ground and mixed with common salt. At that moment the flavour can be added in a simple manner. This, however, is not the case in the preparation of other cheeses.
Dutch patent application 7212074 proposes a process for the preparation of a fat emulsion which, e.g., can be used for the preparation of a cheese- or butter-like product. This preparation starts from an aqueous phase which contains an emulsifier but is free from casein micelles. The emulsifier used is cheese whey, aqueous solutions of caseinates, egg protein or Tween 80. A drawback of using a thus prepared emulsion for the preparation of cheese-like products is that both the taste and the consistency are dissatisfactory. Thus, for instance, Run 17 (Table A) shows that when using soybean oil the consistency of the cheese prepared is insufficient. Furthermore, practice has shown that a cheese prepared using this process is not always free from a typical margarine or oil taste.
German "Offenlegungsschrift" 23 25 133 describes a process for the preparation of a water-in-oil emulsion in which the aqueous phase, the pH of which ranges from 4.2 to 5.5, contains a globular, non-denatured whey protein in a proportion of 0.5-4%. This publication is silent as to the importance of the content of calcium and minerals in the emulsion, which partly explains the necessary presence of an emulsifier.
"Journal of Food Science", Vol. 45 (1980), page 1237 ff., describes a study into the emulsifying properties of whey proteins, the aqueous phase of the emulsions to be studied being formed by dialyzed sour whey. The calcium content in dialyzed sour whey is lower than the minimum calcium content in the emulsions according to the invention. Furthermore, on page 1239 of this publication it is noted that when calcium ions are present in a proportion of 0.1% (9 mmol) unstable emulsions are obtained, as apparently opposed to the inventive concept underlying the present application.
Finally, "Zuivelzicht" 68 (1976) 19, pages 442-445, describes a study into the emulsifying properties of whey protein concentrates obtained by ultrafiltration of sweet cheese whey. Apart from the fact that this publication is silent as to the importance of the content of calcium and minerals, the homogenization pressures used in the preparation of the emulsions described are 20 and 2 MPa, respectively, so that owing to the unduly small sizes of the fat particles contained therein the resulting emulsions are less suitable for the preparation of dairy products.